326 CEETACEOUS PELECYPODA 



genus," says the autlior, "agrees with Nucula in the simple pallial line and internal 

 ligament, and with Mallella in not being nacreous or pearly within, and in general 

 form and character. It belongs to a distinct family between nuculinje and 



MALLETINyE." 



It is possible that this is the recent representant of the fossil Cteiiodonta, 

 connecting in many respects the Nvculivje with the Nuculanidje, for in those fossil 

 forms the pallial line has not been shown to be sinuated, but the position of the 

 cartilage or ligament has also not as yet been satisfactorily traced out. 



3. Clenodonta, Salter, 1851, (Decade Geol. Surv., Great Britain, I; Tellinoiiuja, 

 Hall, ?ex-parte; see Meek and Worthen, Geol. and Pal., Illinois, iii, p. 308). 

 This name has beea proposed as a substitute for Hall's TelUnomya, but unless 

 it has been shown that all the species described by Hall as TelUnomya possess the 

 hinge-teeth of the Nuculidm, which I greatly doubt, there is no suflS.cient reason for 

 identifying both genera. Some of the Tellinomijce noted by Hall and M''C oy certainly 

 are so extremely thin shells that they most improbably belong to the Nuculidm. 

 Taking Cten. coiitracta, Salter, as the type of the genus, it could be characterized as 

 elongately oval, sub-equilateral, smooth, or finely concentrically striated, valves 

 moderately convex, hinge represented by two diverging comb-like denticulated 

 margins without a special hinge area between them and the beak, and below the 

 latter not interrupted by a pit ; ligament apparently external, posterior to the beak. 

 Prom Malletia the shells would seem only to ditfer by a more elongated and more 

 tumid form. 



List of cretaceous species of nuculid.e. 



Among the cretaceous Nucula there are several somewhat elougated aud nearly equilateral 

 forms which apj^ear to resemble Sarejita, but unless the internal structure of these shells has been 

 properly examined no xexx correct generic determination can be attained. The numerous species 

 from the German Planer particularly recpire re-examination. 



For reference of the first 29 species noticed see Pietet and Campiche in Pal. Suisse, III"'' ser., 

 3"" part., p. 416 et seq. 



1-13. — N. planata,* Desh., si>nplex,-[ Desh., suh-triangula,X Koch and Dunk., orata, Mant., 

 (non eaclem Nilsson), yurgitis, P. and Roux, Alhensis, d'Orb., Timotheana, P. and R., Caii/iusia, 

 P. aud R., Arduennemls , d'Orb., pedinata, Sow., Jaccardi, P. aud Camp., liicirgata, Pitt,, 

 .'' oniu/issma, d'Orb. 



The two last named species are referable to the sub-genus Acila. 



14-28. — N. impresaa, (^=Renauxiana, d'Orb.), antiquala, obiusa, apimlata of Sowerby, 

 (lineata, Sow., is a Nuculana), Ramondi, d'Arch., sfrinfida, Rom., (Nord. Kreid., p. 68, 

 pi. viii, fig. 26, non truncata, Nilss.), licussii, d'Orb., sub-del/oidea, d'Orb., coiiciniia, Sow., 

 (183:2)§ Stac/ui, Zitt., redcmpta, Zitt., tox, Gieb., (^teiiera, Mull.),|| ascendeiis, Alth,^^;a«(/a, 



* Why does d'Oibigny (Pal. irtrnq. cret., pi. 300,) represent this and the two other species — CorM«e?ia»o (according to P. 

 and Camp, only a variety of planata) and simplex — on the same plate with distinct fulcra? Have these species an external 

 ligament ? or is it only a lapsi'.s penicilli of tlio artist ? 



+ Non simplex, A. Ad., 1856, a recent shell, the name of which must he changed. 



J The identification with sub-trigona, Rbmer, appears very doubtful, hut I also have no authentic specimens to compare. 



§ Non concinna, A. Ad., 1856, which name must be changed. 



II Miiller' s figure does not appear to he very characteristic. A specimen of this species received from Dr. Bosquet sho»-s 

 a great similarity to Sowerby 's impressa, but this is a decidedly slender and more elongated form. 



If Vide Favre Desc. M. foss. de Lemberg, 1869, p. 119. 



